When tissues (cells) are damaged or infected with invaders (bacteria, fungi, viruses, various types of allergens, etc.), the inflammatory response is associated with various inflammatory mediators and immunocytes in local blood vessels and bodily fluids to exhibit a series of complex physiological responses such as activation of enzymes, secretion of inflammatory mediators, infiltration of bodily fluids, cell migration, tissue destruction, etc., and external symptoms such as erythema, edema, fever, pain, etc. In normal cases, the inflammatory response serves to restore the function of organisms by removing the invaders and regenerating damaged tissues, but if antigens are not removed, or if the inflammatory response is excessive or persistent due to internal substances, it rather promotes damage of mucous membranes, and thus partially develops diseases such as cancer, etc.
In recent years, it has been found that the inflammatory response is one of major mechanisms of causing neurodegeneration. That is, microglial cells that are immunocytes present in the central nervous system may be activated by various exogenous and endogenous substances, and the activated microglial cells produce and release substances such as inflammatory cytokines TNF-α and IL-1β, nitrogen monoxide, prostaglandin, superoxide, etc. (Gao et al., J Neurochem, 81, 1285-97, 2002; Nelson, P T. et al., Ann Med, 34, 491-500, 2002; Griffin, W. S. et al., J Neuroinflammation, 3, 5, 2006). The production of such substances provokes immune responses in the short run, but the excessive or continuous production of the substances induces the death of neighboring nerve cells to cause neurodegeneration. Also, since substances released by dying nerve cells induce the activity of microglial cells again, the neurodegeneration is caught in a continuous vicious circle. In fact, it was reported that the activity of microglial cells is associated with various degenerative nerve diseases such as Alzheimer's disease, Parkinson's disease, Huntington's disease, Lou Gehrig's disease, Creutzfeldt-Jakob disease (CJD), multiple sclerosis, etc.
As such, considering the importance of the neuroinflammatory response in neuro-degenerative diseases, it is possible to treat neuroinflammation and neuro-degenerative diseases that may develop therefrom by reducing a level of expression of proinflammatory mediators in such microglial cells.
Meanwhile, Portulaca grandiflora Hook. is an annual herbaceous plant that belongs to the family Portulacaceae, is native to South America, and consists of approximately 40 species distributed all over the world. The whole plant of Portulaca grandiflora Hook. is referred to as Scutellaria rivularis, which has been used as medicine. It was reported that alfatoxin B1 and cyclophosphamide which are main components of Portulaca grandiflora Hook. have an anti-mutagenesis effect in rodents (Liu et al., Zhongguo Zhong Yao Za Zhi, 1990, 640, 617-622). However, there is no known use of Portulaca grandiflora Hook. in preventing or treating neuroinflammation or neuro-degenerative diseases.